High Blood Pressure in Pregnant Women Linked to Sleep

Maureen Salamon | October 01, 2010 04:47am ET

Mothers-to-be who spend too much or too little time catching zzzz's
early in pregnancy are more likely to have higher blood pressure as
childbirth approaches. The result can lead to grave complications for
both mother and baby, a new study suggests.

Researchers from the University of Washington observed that blood
pressure rose by about 4 points in third-trimester women who reported
sleeping less than six hours or more than 10 hours per night in early
pregnancy.

The study was published today (Oct. 1) in the journal Sleep.

"Those small increases in average blood pressure translate to a
clinically significant risk for preeclampsia," a dangerous condition
involving pregnancy-induced blood pressure spikes and excess protein in
the urine, said study researcher Michelle A. Williams, professor of
epidemiology at the university's School of Public Health.

"The worst cases can lead to very horrible outcomes in mother and
baby," she said, including retinal detachment, seizures or stroke in
women, low birth weight or breathing difficulties in newborns, or death
for either. The study also indicated that very short sleepers — those
who slept less than five hours per night during early pregnancy — were
10 times more likely to develop preeclampsia than those who slept six hours or more.

"It's only a few points, but I do think it's significant. It's just
the tip of the iceberg," said Dr. William Kohler, medical director of
the Florida Sleep Institute and a spokesperson for the American Academy
of Sleep Medicine, who was not involved with the study.

Sleep puzzle

Previous studies have established that high blood pressure
is more prevalent among people of all ages who sleep less than six
hours per night, and the same mechanism is likely to be at work in
pregnant women, Williams told MyHealthNewsDaily.

Because blood pressure is known to dip by an average of 10 percent to 20 percent during sleep, short sleep durations
may raise the average 24-hour blood pressure and heart rate, according
to researchers. This may lead to structural changes that gradually raise
blood pressure long-term.

But Williams said she and other researchers are puzzled about why
longer sleep times during early pregnancy also produced small blood
pressure surges similar to those seen in shorter sleep durations. They
suspect, she said, that undiagnosed, underlying conditions such as sleep
apnea, depression, or insulin resistance create the need for more sleep and may influence the findings.

The norm: 9 hours a night

More than 1,270 healthy pregnant women participated in the study,
which relied on self-reported sleep durations given during interviews
conducted when they were about 14 weeks pregnant. About 20 percent of
the women reported sleep times of nine hours per night, which the
researchers used as the norm.

About 55 percent of the pregnant women reported sleeping seven to
eight hours, while 13 percent slept six hours or less, and 10 percent
slept 10 hours or more.

Williams said her future research will focus on understanding why longer sleep durations lead to small rises in blood pressure.

"Moving forward, large-scale sleep studies should include pregnancy
cohorts so that health-care providers and mothers-to-be can more fully
appreciate the health risks of insufficient sleep," she said.

The research was supported by grants from the Eunice Kennedy Shriver
Institute of Child Health and Human Development of the National
Institutes of Health.